1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member and an electrophotographic apparatus having the electrophotographic photosensitive member.
2. Description of the Related Art
An amorphous deposited film (amorphous-silicon-deposited film) which contains a silicon atom as a main component and further contains a hydrogen atom, a halogen atom and the like has high performance and high durability and causes no pollution when used as a photosensitive member of an electrophotographic photosensitive member to be used in an electrophotographic apparatus, and is commercially used. Electrophotographic photosensitive members having various layer structures with the use of such a deposited film are proposed so as to meet various requirements for the performance. Among them, the electrophotographic photosensitive member provided with a surface layer has superior abrasion resistance, charge retentivity and environment resistance, and is generally used.
Along with the development of the colorization of the electrophotographic apparatus, a finer image is formed, the image is exposed with rays having shorter wavelengths, and the surface layer having high transmissivity to the rays having the shorter wavelengths is required. A technology (Japanese Patent Application Laid-Open No. H06-83091) of forming the surface layer from an aluminum oxide material containing zinc is reported as a technology relating to the surface layer having a large band gap to rays having such shorter wavelengths.
Furthermore, when the processing speed of forming an image is increased according to the request of increasing a printing speed of the electrophotographic apparatus, the load for the electrophotographic photosensitive member increases, so that when the image is repeatedly formed with the use of a conventional electrophotographic photosensitive member at a high speed for a long period of time, various problems arise. Specifically, a part of the surface layer is lifted up from a photoconductive layer in a fine region with a diameter of approximately several micrometers, and as a result, the outline of the image occasionally spreads and becomes unclear to cause image blurring, or the abrasion amount of the surface layer occasionally suddenly increases during use. In addition, a so-called ghost may be produced, which is a phenomenon that an image pattern formed right before is formed and overlapped on the present image, or an image quality may be lowered due to a phenomenon that a toner having deposited on the surface of the electrophotographic photosensitive member is fusion-bonded with the surface. The electrophotographic photosensitive member with the use of the amorphous-silicon-deposited film originally forms a sharp latent image, so that the image blur and the ghost tend to outstand as the degradation of the image for the electrophotographic photosensitive member. From that point of view, the electrophotographic photosensitive member having the surface layer formed from the above described aluminum oxide material containing zinc is difficult to be applied to an electrophotographic apparatus which forms the image at the high speed.